Thermally actuated frequency control



Patented Aug. 2, 1949 THERMALLY ACTUATED FREQUENCY CONTROL 7 Edwin T. Jaynes, Garden City, N. Y., assignor to The Sperry Corporation, a corporation of Delaware Application January 24, 1944, Serial No. 519,585

1? Claims.

This invention relates to frequency control and is particularly concerned with electrical or thermally sensitive frequency control arrangements for hollow resonator apparatus.

In a thermally responsive hollow resonator frequency control system wherein expansible and contractible struts or wires are electrically heated, it is desirable to maintain the system substantially at or near a selected normal operating frequency approximately at the middle of the range in of frequency control. In prior systems within my knowledge, this has usually been accomplished by maintaining a strut or wire constantly energized so as to provide a condition of substantially dynamic balance in the system at the selected resonator frequency. The chief objections to these prior systems are that they continually use power, and that the adjustment of the circuits is lost when the receiver or other apparatus using the system is turned off.

- It is a major object of the invention to provide a novel electrically energized frequency control system for hollow resonator apparatus having arrangements whereby the resonator frequency may be independently preset at a desired operating point within a preselected control range without electrical energization of the system.

A further object of the invention is to provide a hollow resonator frequency control system embodying independently actin thermally responsive frequency control members for varying the resonator frequency in opposite directions and novel associated arrangements for adjusting the resonator frequency independently of energization of said thermal responsive members.

A further object of the invention is to provide a novel assembly of electrically and manually operable frequency controls for hollow resonator apparatus. 7 I It is a further object of the invention to provide an automatic frequency control system wherein the device of Figure 1 may be used; and Figure 3 is a wiring diagram illustrating further details of part of the automatic frequency control system of Figure 2.

Referring first to Figure 1, the illustrated hollow resonator device comprises a pronged base ll of the usual vacuum tube type and a cathode surrounding structure consisting of a glass collar l2 sealed to base II and a metal collar l3 sealed to collar l2.

At its upper end, collar I3 is formed with a reduced coaxial hollow tubular extension M which is secured to a cylindrical hollow conductive resonator body I5. Collar l3 and resonator body 15 have secured thereto parallel spaced radial flanges l6 and I1, respectively, which extend normal to the resonator axis. Above flange IT, a metal collar I8 is secured to resonator l5, and the upper end of collar I8 is sealed and closed by a glass end cap l9.

Base H, collars l2 and I3, tube l4, resonator l5, collar l8 and cap l9 constitute a vacuum sealed envelope, and the cathode (not shown) projects a stream of electrons along the resonator axis through resonator I5. A reflector electrode 2| mounted on a conductor 22 sealed in cap 19 and fixed to external terminal 23 is centered with the resonator axis.

As illustrated in section in Figure l, the upper end of tube I4 is fixed to a flexible end wall 24 of resonator l5 and'extends through wall 24 to provide a reentrant hollow pole 25 within resonator l 5. Parallel apertured grids 26 and 27 are mounted in adjacent spaced relation upon the upper end of pole 25 and in a suitable central aperture in the relatively stiff upper end wall 28 of resonator 15 which is rigid with flange l1. Thus, grids 26 and 21 are rigid with flanges l6 and I1 respectively and are eflectively flexibly interconnected by wall 24.

Flanges I6 and I1 are interconnected by a tension spring 29. A pair of rigid parallel struts 3| having their opposite ends reduced for interfittin with suitable locating recesses on flanges I? and I! are interposed between flanges l6 and I Only one strut 3| is illustrated in Figure 1 since the other strut is directly behind that shown and equidistant from spring 29. Since struts 3| are disposed on the same side of the center line of the device as spring 29, it is clear that flanges I6 and I! are fulcrumed about the strut ends and that spring 29 tends to rock flanges l6 and I! about parallel lateral axes substantially perpendicular to the resonator axis in such manner as to increase the resonator grid gap. This tendency of sprin 29 to separate grids 26 and 2! is opposed and controlled by the structure at the right side of Figure 1.

Flange l6 has secured thereto, as by bolt 32, a bracket 33 upon which is rigidly mounted a hollow tube 34. The lower end of tube 34 is closed by a plug 35 which is centrally tapped to receive an adjustable threaded element 36. A suitable locknut 31 locates element 36 in any position of axial displacement.

A rigid support member 38 which freely extends radially into tube 34 through a suitable aperture 39 is fixed to flange I1, as by bolt 40. A suitable closure 4| is provided for the top end of tube 34. Diametrically opposite aperture 39, tube 34 is provided with an aperture 42 which is formed with a knife edge portion 43 serving as a fulcrum for one arm of a bifurcated lever 44 extending through aperture 42. The other arm of lever 42 is engaged by an adjustable threaded member 45 mounted on an upstanding part of bracket 38.

A rigid body 46 of glass or like insulating material is provided with spaced imbedded stiff conductor rods 41 and 41, and the oppositely projecting ends of rods 41 and 41' are secured as by soldering or welding to the lower ends of flexible conductor wires or strips 48 and 49 respectively which have their upper ends anchored respectively to support 38 and lever 44 as illustrated. A tension spring is interposed between body 46 and adjustable element 36, so as to maintain both conductors 48 and 49 taut and to oppose spring 29.

Conductors 48 and 49 have their lower ends electrically connected to external leads 52 and 53 respectively extending through suitable insulated bushings on tube 34. The upper ends of conductors 48 and 49 are grounded'to the resonator frame, and'leads. 52 and 53 are connected to suitable separate energy sources for selectively independently passing and/or varying heating current through conductors 48 and 49 as will be described below in an important example.

In operation, the electron stream from the cathode initially traverses the gap between resonator grids 26 and 21 and is then returned by reflector 2| into resonator l5, so as to excite and maintain an oscillatory electromagnetic field in resonator l5. Accepted theories of this action based on electron velocity modulation principles are explained fully in United States Letters Patent No. 2,250,511 to which reference is made for further details. Microwave energy is extracted from the resonator field as by the usual concentric line terminal assembly 52.

It is known that changes in volume and shape of resonator |5, such for example as may be occasioned by changes in the spacing of grids 26 and 21, result in corresponding variations in resonator frequency. This property is utilized in the present invention.

Manual control of the resonator frequency is obtainable by adjustment of member 45. When member 45 is turned to cause clockwise rotation of lever 44, this motion is transmitted through conductor 49 to displace body 46 upwardly against the tension of spring 5|. The resulting slackness of conductor 48 is promptly taken up by the action of spring 29 in relatively rocking flanges |6 and H. Where the device is seated in a stationary socket for example, under these conditions spring 29 will cause flange H to rock counterclockwise about its fulcrum thereby increasin the gap between grids 26 and 21 and increasing the resonator frequency.

Conversely, when member 45 is turned in the opposite direction, lever 44 is. free to rock counterclockwise under the pull of spring 5| so that body 46 is displaced downwardly, thereby relatively rockingflanges I6, l1. Again where the device is seated in a stationary socket, the downward motion of body 46 transmitted by conductor 48 causes flange IT to rock clockwise about its fulcrum against the opposition of spring 29. Spring 5| is therefore selected of sufficient strength relative to spring 29 and the leverage of the associated parts to accomplish this operation.

The tension of spring 5| is preset by adjustment of element 36, and this maintains the parts in a tight assembly very sensitive to control forces. In practice, the tension of spring 5| is about twice that of conductor 48 because of the pull of sprin 29.

Assume that conductor 49 is heated hotter than conductor 48, as by passage of electric current therealong. Conductor 49 is elongated more than conductor 48, thereby permitting spring 5| to downwardly displace body 46, conductor 48, flange I1 and grid 21 to decrease the frequency of resonator l5. Reversely, when conductor 48 is heated more than conductor 49, conductor 48 elongates more than conductor 49, thereby permitting spring 29 to effect upward displacement of grid 21 and consequent increase in the frequency of resonator I5.

Under practical operating conditions, it is possible to first adjust the resonator frequency to a predetermined operating point by the manual control at 45, and then speedily effect desired variations in the resonator frequency in opposite directions from that operating point by suitable energization of conductors 48 and/or 49.

The above described device is especially useful in an automatic frequency control system such as illustrated in Figures 2 and 3 and described below.

Figure 2 illustrates a representative system wherein the invention is usable and wherein the output frequency of a local oscillator source 54 is automatically controlled to maintain a desired intermediate frequency. Source 54 may be the device of Figure 1, and source 55 may be any similar device or high frequency wave receiver.

The outputs of sources 54 and 55 are combined in mixer 56, and the intermediate frequency output of mixer 56 is amplified at 51 and introduced into a discriminator 58. Signals from discriminator 58 are fed into a frequency control circuit 59 which in turn is connected to energize suitable frequency control elements in source 54, such as conductors 48 and 49.

Figure 3 illustrates a detailed circuit arrangement usable for carrying out this phase of the invention.

Discriminator transformer primary 6| is connected across the output of intermediate frequency amplifier 51 in parallel with variable condenser 62 by which the primary transformer circuit may be tuned to the desired intermediate frequency. A reference voltage from primary BI is applied through phase shifting condenser 6|] to the midpoint of transformer secondary 63.

Discriminator transformer secondary 63 is connected in parallel with a variable condenser 64, by which the secondary transformer circuit may also be tuned to the desired intermediate frequency. Opposite ends of secondary 63 are connected to the anodes of diode rectifiers 65 and 66, and the cathodes of rectifiers 65 and 66 are connected to an impedance 61 through equal resistors 68 and 69, respectively, and to ground through equal output resistors 10 and 1 I. Alternating current bypass condensers I2 and I2 are provided across resistors 68 and 69 respectively, and the center of transformer secondary 63 is con nected to the other side of impedance 61.

The output of discriminator 58 controls the frequency control circuit which comprises substantially the remainder of Figure 3 except conductors 48 and 49.

Alternating voltage for the control circuit is derived from a source I9, which is connected through condensers I4 and I5 to the control grids I6, II of variable-mu pentodes I8 and I9 respectively. The output of discriminator 58 is likewise connected to grids I6, 11 through resistors BI and 82 which impede flow of alternating current to the discriminator. Condensers I4 and I5 block against flow of direct current to source I3.

The cathodes of pentodes I8, I9 are interconnected by a resistor 83 connected through adjustable taps 84 and 85 to grounded resistor 86. Adjustment of tap 84 varies the relative bias of pentodes I8 and I9, while adjustment of tap 85 varies the bias of these tubes concomitantly. The purpose of these adjustments will appear later.

The screen grids of pentodes I8, I9 are connected together and through screen dropping resistor 81 to a suitable high voltage plate circuit supply indicated at 89. A voltage regulator tube 89 is provided to prevent the screen voltage of tubes I8 and I9 from varying with control grid bias, and to avoid degeneration due to alternating current on the screen grids.

The anodes of pentodes I8 and I9 are connected through respective load resistors 9| and 92 to plate supply 88. Coupling condensers 93, 94 connect resistors 9|, 92 to input resistors 95, 96 respectively of a power amplifier stage including conventional tetrodes 91 and 98. The common junction of input resistors 95, 96 is connected through grid biasing battery 99 to the cathodes of tetrodes 91, 98.

Input resistors 95, 9B are connected to control grids I9I, I92 of tetrodes 9I, 98. The anodes of tetrodes 91, 98 are connected through output transformer primaries I93, I94 to a common screen grid lead which in turn is connected to a high voltage plate supply I95 for the power amplifier stage. resistances electrically, are connected across output transformer secondaries I96, I91 for receiving energy from opposite sides of the amplifier stage.

In operation of the circuit of Figure 3, the currents in discriminator output resistors 61, 68 provide unidirectional voltage drops which are applied to control grids I9 and 7! respectively, thus varying the relative bias of the pentodes I8 and 19. Operation of this type of discriminator is well known, the relative values of the voltage drops across resistors 69 and 69 depending upon the direction and degree of departure from the desired intermediate frequency. Source I3 superposes an equal alternating voltage on each of control grids I6 and I1.

When the output frequency of amplifier 51 is that for which discriminator 58 is tuned, the currents in resistors 68, 69 are equal and opposite, thereby applying no voltage to grids I6 and 11. Under such conditions pentodes l8 and I9 are equally conductive, provided tap 84 is correctly adjusted; and the gain of tubes I8 and 19 may be varied by means of tap 85. In particular these tubes may be made to have very low gain.

Conductors 48 and 49, which are Under these conditions the signals applied to grids I9! and I92 of tetrodes 91 and 98 are equal and may be made very small if desired. Hence conductors 48 and 49 are equally energized and there is no tendency for the frequency of the device in Fig. 1 to change.

However; suppose that the intermediate frequency departs in a direction such that the current through resistor 88 is larger than the current through resistor 69. The action of resistanoe network 68, 69, I9, II, 8I, 82 is then to decrease the bias on pentode I8 and increase the bias on pentode 19. Due to the well-known action of variable-mu tubes, this increases the gain of pentode I8 and decreases the gain of pentode i9. Conductor 48 is then heated more than conductor 49. Referring back to the operation of Figure 1, the above described increased heating of conductor 98 produces an increase in the frequency of resonator I5.

When the output frequency of amplified 5! departs in the opposite direction, this results in increase in the gain of pentode I9 and decrease in the gain of pentode I8 and conductor 49 is now heated more than conductor 48, so as to cause reduction in the frequency of resonator I5.

Adjustment of tap 95 simultaneously controls the amplitude of the heating current deliverable to both conductors 98 and 49, and this adjustment is made in different ways depending on what characteristics one desires of the system. If low power consumption is important, tap 85 should be set so that the gain of pentodes I9 and i9 is very low when the intermediate frequency at 51 is at the correct value. Practically no power is then delivered to either of conductors 48 and 49. Power will be delivered to conductors 48 and 49 only to correct frequency deviations, and only one conductor at a time will be heated. If, on the other hand, one desires the greatest possible speed of response of the automatic frequency control system, a further factor of almost two can be obtained by setting tap 85 so that the voltage gain of the pentodes is sufiicient to result in power being fed to conductors 48 and 49 continuously, so that any frequency deviations will cause one conductor to expand and the other to contract an equal amount, thus substantially multiplying the eiTect which would be obtained by having only one conductor at a time respond.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in. the above description or shownin the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. High frequency apparatus comprising a hollow resonator having relatively movablemeans for varying the frequency of said resonator, separately acting thermally sensitive longitudinally expansible means operably connected to said relatively movable means, the longitudinal expansion of said expansible means moving said movable means to selectively independently vary the resonator frequenc in opposite directions, one of said expansible means having an end connected mechanically to one of said movable means, the other of said expansible means having an end connected mechanically to the other of said movable means, the other ends of each of said expansible means being connected to an insulating 75 mounting means and manually adjustable means in said apparatusoperably connected to said movable means for selectively independently varying the resonator frequency regardless of energization of said thermally sensitive means.

2. The apparatus defined in claim 1, wherein said thermally sensitive longitudinally expansible means comprises two separately energizable electrical conductors operably connected to said movable means.

3. High frequency apparatus comprising a hollow resonator having two parts which are relatively movable for varying the frequency of said resonator, independently actuatable separately acting axially expansible and contractible means, one having an end connected mechanically to one of said parts, the other having an end connected mechanically to the other of said parts, the other ends of each of said means being connected to an insulating mounting means for selectively varying the resonator frequency in opposite directions relative to a predetermined reference point, and means in said apparatus for selectively independently varying the resonator frequency for shifting said reference point.

4. High frequency apparatus comprising a hollow resonator having wall portions which are relatively movable for varying the frequency of said resonator, a pair of thermally sensitive members operably connected to said wall portions and selectively relatively energizable for independently varying the resonator frequency in opposite directions, one of said members having an end connected mechanicall to one of said portions, the other of said members having an end connected mechanically to the other of said portions, the other ends of each of said members being connected to an insulating mounting means, and manually operable means including an ad- ,iustable lever in said apparatus operably connected to said hollow resonator for varying the resonator frequency independently of the energization of said members.

5. High frequency apparatus comprising a hollow resonator device having parts which are relatively movable for varying the frequency of said resonator, separate longitudinally expansible and contractible frequency control members, one of said members having an end connected mechanically to one of said parts, the other of said members having an end. connected to the other of said parts, the other ends of each of said members being connected to an insulating mounting means, said members being selectively actuatable or relatively moving said parts in a direction substantially parallel to the expansion and contraction of said means and independently varying the resonator frequency in opposite directions, and further frequenc control means also operably connected to said parts for varying the resonator frequency independently of said actuation of said separate frequency control means.

6. The apparatus defined in claim 5, wherein said separate frequency control means constitute portions of said further frequency control means.

7. High frequency apparatus comprising a hollow resonator device having parts which are relatively movable for varying the frequency of said resonator, separate thermally sensitive longitudinally expansible and contractible members, one of said members. having an end connected mechanically to one of said parts, the other of said members having an end connected to the other of said parts, the other ends of each of said members being connected to an insulating mounting means, said members being cperably connected'to said parts and selectively energizable by the passage of electric current therethrough for independently varying the frequenc of said resonator in opposite directions, and means in said apparatus for varying said resonator frequency independently of energization of said members.

8. The apparatus defined in claim 7, wherein said last named means comprises motion transmitting mechanism including said thermally sensitive members.

9. High frequency apparatus comprising a ho]- low resonator having a pair of wall portions which are relatively movable for varying the frequency of said resonator, laterally extending members rigid with said respective wall portions, a mounting body resiliently connected to one of said members, a pair of thermally sensitive electrical conductors having corresponding ends anchored in spaced relation on said body so as to be electrically insulated from each other at said ends, means fixing the other end of one of said conductors to one of said members, and adjustable lever means between the other end of said other conductor and the other of said members.

10. The apparatus defined in claim 9, wherein said mounting body comprises a bod of insulating material.

11. High frequency apparatus comprising a tunable hollow resonator device having relatively movable wall portions, a first thermally sensitive member operably connected to said device and energizable for varying the resonator frequency in one direction, one end of said first member being connected mechanically to one of said portions a second thermally sensitive member operably connected to said device and energizable for varying the resonator frequency in the oppositedirection, one end of said second member being connected mechanically to the other of. said wall portion, the other ends of both of said first and second members being connected to an insulating mounting means, and manually operable means embodying motion transmitting mechanism containing said thermally sensitive members for varying the resonator frequency independently of the degree of energization of said thermally sensitive members.

12. High frequency apparatus comprising a hollow resonator device having two parts which are relatively movable for varying the frequency of said resonator, two flexible thermally responsive members in said apparatus each having one end connected to a respective one of said parts, means for mounting the other ends of said members in electrically insulated relation, and manually operable means for adjusting said mounting means in opposite directions for independently varying said resonator frequency.

13. The apparatus defined in claim 12. wherein said adjusting means comprises means resiliently connecting said mounting means to one of said parts and an adjustable rockable lever interposed between one of said members and one of said parts.

14. An electron discharge device comprising a hollow resonator having relatively movable electron permeable wall portions mounted in alignment to permit passage of an electron stream through the resonator field in the gap between said portions, a mounting member resiliently connected to one of said wall portions, two thermally sensitive expansible and contractible flexible conductors having corresponding ends secured in electrically insulated relation to said mounting member, means securing the other ends of said flexible conductors to said respective wall portions, lateral flanges rigid with said respective wall portions, and means mounting said flexible conductors and securing means on said flanges.

15. Electron discharge apparatus comprising means for producing a stream of electrons, an adjustable hollow resonator having relatively movable portions and positioned along the path of said stream in energy-exchanging relation therewith, an envelope providing a vacuum-tight enclosure for said stream, a. pair of thermally sensitive expansible and contractible conductors carried on said envelope exteriorly thereof, each of said conductors having one end thereof connected to a respective one of said movable portions, adjustable means mounting the other ends of said conductors in electrically insulated relation, and means coupled to said conductors and providing for electrical energization thereof, whereby said resonator is adjustable in opposite directions in accordance with alterations in length of said conductors produced by said electrical energization.

16. The electron discharge apparatus defined in claim 15 further having manuall operable means connected at one end of one of said conductors for adjusting said resonator independently of the energization of said pair of conductors.

17. High frequency apparatus comprising a hollow resonator having relatively movable portions, two thermally sensitive extensible and contractible members, one of said members having an end connected mechanically to one of said portions, the other of said members having an end connected to the other of said portions, the

other ends of each of said members being connected to an insulating mounting body, means for varying the temperature of said thermally sensitive means to produce variations in the length thereof and corresponding variations in the resonant frequency of said resonator, and manually operable means, including motion transmitting means embodying said thermally sensitive means, for adjusting the relative spacing between said relatively movable means whereby variations in the resonant frequency of said resonator ma be produced independently of said thermally sensitive means.

EDWIN T. JAYNES.

REFERENCES CITED The following referemces are of record in the file of this patent:

UNITED STATES PATENTS 

